Are We Looking at Each Other?

From our most favorite web-site, The Astronomy Picture of the Day:


2007 April 26



See Explanation.  Clicking on the picture will download
the highest resolution version available.

Gliese 581 and the Habitable Zone
Credit:
Stephane Udry, Michel Mayor
(Geneva Obs.)
et. al,
Image: DSS,
Skyview

Explanation:

The faint, unremarkable star centered in this
skyview
is Gliese 581,
a mere 20 light-years away toward the constellation
Libra.

But
astronomers
are now
reporting
the discovery
of a remarkable
system of three planets orbiting Gliese 581, including the
most earth-like planet found beyond our solar system.

Gliese 581 itself is not a sun-like star, though.

Classified as a
red
dwarf
, the star is much smaller and colder than the Sun.

Still, the smallest planet known to orbit the star is estimated to
be five times as massive as Earth with about 1.5 times Earth’s
diameter.

That super-earth
orbits once every 13 days, about 14 times closer
to its parent star than the Earth-Sun distance.

The close-in orbit around the cool star implies a mean surface
temperature of between 0 and 40 degrees C – a range over which water
would be liquid – and places the
planet in
the red dwarf’s
habitable zone.

Are they looking at us while we are looking at them?

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